Added premake5 caching to GH Actions. #12

	name: Compile

	on:
	push:
	branches: [ master ]
	pull_request:
	branches: [ master ]

	jobs:
	build:
	runs-on: ubuntu-latest

	steps:
	- uses: actions/checkout@v2
	with:
	fetch-depth: 0

	- name: Cache Premake
	id: cache-premake
	uses: actions/cache@v2
	with:
	path: \|
	premake5
	key: ${{ runner.os }}-premake-${{ hashFiles('**/premake5.lua') }}

	- name: Install Premake
	if: steps.cache-premake.outputs.cache-hit != 'true'
	run: \|
	wget https://github.com/premake/premake-core/releases/download/v5.0.0-alpha16/premake-5.0.0-alpha16-linux.tar.gz
	tar -xzvf premake-5.0.0-alpha16-linux.tar.gz
	sudo mv premake5 /usr/local/bin/

	- name: Install Clang
	run: \|
	sudo apt update
	sudo apt install -y clang

	- name: Set CC and CXX environment variables
	run: \|
	echo "CC=clang" >> $GITHUB_ENV
	echo "CXX=clang++" >> $GITHUB_ENV

	- name: Run Premake
	run: premake5 gmake

	- name: Compile Project
	run: make config=debug CC=clang

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